Caroline Wozniacki is a doubt for the French Open after she was forced to withdraw from her second round match with Anabel Medina Garrigues at the Internazionali BNL d'Italia due to injury.

The year's second grand slam gets underway at Roland Garros on May 27, leaving Wozniacki less than two weeks to recover from Wednesday's blow. She trailed Garrigues 6-4 4-0 when the hand was offered, having had treatment through the contest.

Wozniacki called for the trainer during the first set of her match in Rome, but she continued to struggle on, often wincing as she attempted to play through the pain.

Clearly the problem was restricting the former world No. 1 as she fell a set behind, before being broken in back-to-back service games in the second. It was at that point that she retired from the contest in front of watching boyfriend Rory McIlroy.

Elsewhere, Serena Williams overcame an early scare to defeat Nadia Petrova in three sets to make it into the next round of the competition.

Petrova was the only player to create break points in the first set - converting one of three for 6-4 - but crucially failed to repeat the feat in the second set after engineering the first five break points of the stanza.

That opened the door for Serena, who converted her first break point opportunity to go 3-1 ahead - as she wrestled control of the match's momentum on the way to an eventual 4-6 6-2 6-3 victory that took over two hours.

Serena's sister Venus Williams also won her match on Wednesday, although not after the wildcard also had to survive a scare. But, after edging a first-set tiebreak against Ekaterina Makarova, she ran wild on the way to an eventual 7-6(7) 6-1 triumph.

Later in the day, Victoria Azarenka breezed into the next round with a 6-1 6-2 victory over Israel's Shahar Peer.

Wozniacki was not the only big name to exit the competition on Wednesday, with third seed Agnieszka Radwanska beaten 6-4 4-6 6-1 by Petra Cetkovska. Defeat was also tasted by seventh seed Marion Bartoli, who was broken six times in a 6-3 6-1 loss to Julia Goerges.

Plenty of talent remains in the competition, though, with wins for fifth seed Sam Stosur and eighth seed Li Na. Both advanced in straight sets and will be expected to reach the latter stages of the tournament.